The invention relates to an antenna switch for wireless antenna diversity telecommunications devices with two antennas.
Wireless antenna diversity telecommunications devices are for example, wireless TDMA (Time Division Multiple Access) telecommunications devices according to the DECT standard (Digital European Cordless Telecommunication; cf. Nachrichtentechnik Elektronik (Telecommunication Electronics), Berlin, year 42, No. 1, 1-2/1992, pages 23 to 29, U. Pilger: "Struktur des DECT-Standards") or according to the GSM Standard (Groupe Speciale Mobile or Global Systems for Mobile Communication; cf. Informatik Spektrum (Computing Publication), Springer Verlag Berlin, year 14, 1991, No. 3, pages 137 to 152, A. Mann: "Der GSM-Standard--Grundlage fur digitale europaische Mobilfunknetze"). Wireless antenna diversity telecommunications devices with two antennas are known from International Application WO/94/10812 (FIGS. 1 and 2 with the associated description). The known antenna diversity radio transceiver has an antenna switch with two in-series switching elements (Diversity Switch DS and T/R Switch T/R-S according to FIG. 2 in International Application WO 94/10812) for switching over between the two antennas (implementation of "antenna diversity") and switching over between transmission and reception mode of the transceiver.
FIG. 1 shows the basic circuit diagram of such a cascade antenna switch 1, which has two in-series switching elements, a first switching element SE-I and a second switching element SE-II. These switching elements SE-I and SE-II switch through selectively a first signal path SW1 from a transmitter TR to a first transmission/reception antenna A1, a second signal path SW2 from the transmitter TR to a second transmission/reception antenna A2, a third signal path SW3 from a receiver RE to the first transmission/reception antenna A1 and a fourth signal path SW4 from the receiver RE to the second transmission/reception antenna A2. With this cascade configuration, switching losses occur at each switching element SE-I, SE-II for the implementation of the switching functions described above. These switching losses unnecessarily reduce the transmission power irradiated and the reception sensitivity of the transceiver.